A known operation input detection device detects an operation input performed on an operation input unit, which is arranged on a vehicle surface, based on a sensor output of a capacitance sensor that changes when a detection subject moves toward and away from the operation input unit. For example, patent document 1 discloses a configuration that alloys a door of the vehicle to be locked and unlocked in a non-contact manner by detecting the hand of a user proximate to a door handle of the vehicle. This improves the convenience.
Further, in such a non-contact sensor device, external noise may be superposed on the sensor output. The sensor output on which the external noise is superposed may be erroneously recognized as the approach of a detection subject.
Patent document 2 describes an example of a method for separating external noise with the Fourier transform. This ensures high reliability without decreasing the detection sensitivity.